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Sep 23, 2013
09/13

by
Dan Hooper; Pasquale Blasi; Pasquale Dario Serpico

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Recent results from the PAMELA satellite indicate the presence of a large flux of positrons (relative to electrons) in the cosmic ray spectrum between approximately 10 and 100 GeV. As annihilating dark matter particles in many models are predicted to contribute to the cosmic ray positron spectrum in this energy range, a great deal of interest has resulted from this observation. Here, we consider pulsars (rapidly spinning, magnetized neutron stars) as an alternative source of this signal. After...

Source: http://arxiv.org/abs/0810.1527v2

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Sep 18, 2013
09/13

by
Karin I. Oberg; Ewine F. van Dishoeck; Harold Linnartz

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A longstanding problem in astrochemistry is how molecules can be maintained in the gas phase in dense inter- and circumstellar regions. Photodesorption is a non-thermal desorption mechanism, which may explain the small amounts of observed cold gas in cloud cores and disk mid-planes. This paper aims to determine the UV photodesorption yields and to constrain the photodesorption mechanisms of three astrochemically relevant ices: CO, N2 and CO2. In addition, the possibility of co-desorption in...

Source: http://arxiv.org/abs/0809.1333v2

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Sep 21, 2013
09/13

by
Patrick Rice; Jim Harrington

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Decoy state protocols are a useful tool for many quantum key distribution systems implemented with weak coherent pulses, allowing significantly better secret bit rates and longer maximum distances. In this paper we present a method to numerically find optimal three-level protocols, and we examine how the secret bit rate and the optimized parameters are dependent on various system properties, such as session length, transmission loss, and visibility. Additionally, we show how to modify the decoy...

Source: http://arxiv.org/abs/0901.0013v2

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Sep 22, 2013
09/13

by
Andrey Doroshkevich; Jakob Hansen; Igor Novikov; Alexander Shatskiy

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We investigate numerically the process of the passage of a radiation pulse through a wormhole and the subsequent evolution of the wormhole that is caused by the gravitational action of this pulse. The initial static wormhole is modeled by the spherically symmetrical Armendariz-Picon solution with zero mass. The radiation pulses are modeled by spherically symmetrical shells of self-gravitating massless scalar fields. We demonstrate that the compact signal propagates through the wormhole and...

Source: http://arxiv.org/abs/0812.0702v2

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Sep 22, 2013
09/13

by
Manodeep Sinha; Kelly Holley-Bockelmann

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Galaxy merger simulations have explored the behaviour of gas within the galactic disk, yet the dynamics of hot gas within the galaxy halo has been neglected. We report on the results of high-resolution hydrodynamic simulations of colliding galaxies with hot halo gas. We explore a range of mass ratios, gas fractions and orbital configurations to constrain the shocks and gas dynamics within the progenitor haloes. We find that : (i) A strong shock is produced in the galaxy haloes before the first...

Source: http://arxiv.org/abs/0901.3782v1

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Sep 18, 2013
09/13

by
John R. Klein; Bruce Williams

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This is the second in a series of papers. Here we develop here an intersection theory for manifolds equipped with an action of a finite group. As in our previous paper, our approach will be homotopy theoretic, enabling us to circumvent the specter of equivariant transversality. This theory has applications to embedding problems, equivariant fixed point theory and the problem of enumerating the periodic points of a self map of a compact smooth manifold.

Source: http://arxiv.org/abs/0803.0017v3

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Sep 21, 2013
09/13

by
Jian Zhou; Feng Yuan; Zuo-tang Liang

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We study the azimuthal asymmetry in the Drell-Yan lepton pair production in hadronic scattering processes at moderate transverse momentum region, taking into account the contributions from the twist-three quark-gluon correlations from the unpolarized hadrons. The contributions are found to dominate the asymmetry, and are not power suppressed by q_\perp/Q at small q_\perp where q_\perp and Q are the transverse momentum and invariant mass of the lepton pair. Accordingly, the Lam-Tung relation...

Source: http://arxiv.org/abs/0901.3601v1

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Sep 22, 2013
09/13

by
Neven Simicevic

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The time-dependent Dirac equation is solved using the three-dimensional Finite Difference-Time Domain (FDTD) method. The dynamics of the electron wave packet in a scalar potential is studied in the arrangements associated with the Klein paradox: potential step barriers and linear potentials. No Klein paradox is observed.

Source: http://arxiv.org/abs/0901.3765v1

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Sep 21, 2013
09/13

by
Kouji Nakamura

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In addition to the second-order Einstein equations on four-dimensional homogeneous isotropic background universe filled with the single perfect fluid, we also derived the second-order perturbations of the continuity equation and the Euler equation for a perfect fluid in gauge-invariant manner without ignoring any mode of perturbations. The consistency of all equations of the second-order Einstein equation and the equations of motion for matter fields is confirmed. Due to this consistency check,...

Source: http://arxiv.org/abs/0901.3638v1

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Sep 18, 2013
09/13

by
Indira Chatterji; Cornelia Drutu; Frederic Haglund

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We prove the existence of a close connection between spaces with measured walls and median metric spaces. We then relate properties (T) and Haagerup (a-T-menability) to actions on median spaces and on spaces with measured walls. This allows us to explore the relationship between the classical properties (T) and Haagerup and their versions using affine isometric actions on $L^p$-spaces. It also allows us to answer an open problem on a dynamical characterization of property (T), generalizing...

Source: http://arxiv.org/abs/0704.3749v4

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Sep 21, 2013
09/13

by
Max Lein; M. Mantoiu; S. Richard

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In previous articles, a magnetic pseudodifferential calculus and a family of C*-algebras associated with twisted dynamical systems were introduced and the connections between them have been established. We extend this formalism to symbol classes of H\"ormander type with an x-behavior modelized by an abelian C*-algebra. Some of these classes generate C*-algebras associated with the twisted dynamical system. We show the relevance of these classes to the spectral analysis of...

Source: http://arxiv.org/abs/0901.3704v1

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Sep 22, 2013
09/13

by
Tadahiro Miyao; Herbert Spohn

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The retarded van-der-Waals potential, as first obtained by Casimir and Polder, is usually computed on the basis of nonrelativistic QED. The hamiltonian describes two infinitely heavy nuclei, charge $e$, separated by a distance $R$ and two spinless electrons, charge $-e$, nonrelativistically coupled to the quantized radiation field. Casimir and Polder use the dipole approximation and small coupling to the Maxwell field. We employ here the full hamiltonian and determine the asymptotic strength of...

Source: http://arxiv.org/abs/0901.3678v1

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Sep 21, 2013
09/13

by
Alin Bostan; Muhammad Chowdhury; Joris van der Hoeven; Eric Schost

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We study the cost of multiplication modulo triangular families of polynomials. Following previous work by Li, Moreno Maza and Schost, we propose an algorithm that relies on homotopy and fast evaluation-interpolation techniques. We obtain a quasi-linear time complexity for substantial families of examples, for which no such result was known before. Applications are given to notably addition of algebraic numbers in small characteristic.

Source: http://arxiv.org/abs/0901.3657v1

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Sep 22, 2013
09/13

by
Andrzej J. Buras; Diego Guadagnoli

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We reappraise the question whether the Standard Model, and Minimal Flavor Violating (MFV) models at large, can simultaneously describe the observed CP violation in the K- and Bd-systems. We find that CP violation in the Bd-system, measured most precisely through (sin 2 beta)_{J/psi Ks}, implies |epsilon_K^{SM}| = 1.78(25) x 10^{-3} for the parameter epsilon_K, measuring indirect CP violation in the K-system, to be compared with the experimental value |epsilon_K^{exp}| = 2.23(1) x 10^{-3}. To...

Source: http://arxiv.org/abs/0901.2056v2

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Jul 22, 2013
07/13

by
C. Fechner; P. Richter

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We present a study of NV absorption systems at 1.5 < z < 2.5 in the optical spectra of 19 QSOs. Our analysis includes both absorbers arising from the intergalactic medium as well as systems in the vicinity of the background quasar. We construct detailed photoionization models to study the physical conditions and abundances in the absorbers and to constrain the spectral hardness of the ionizing radiation. The rate of incidence for intervening NV components is dN/dz = 3.38 +/- 0.43,...

Source: http://arxiv.org/abs/0807.4638v2

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Sep 21, 2013
09/13

by
C. M. Chaves; A. Troper

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We study the possibility of ferromagnetism in metals. The metal is described by two hybridized bands one of which includes Hubbard correlation whereas the other is uncorrelated. We parametrize the ratio of the band widths and their centers as well. The original Hamiltonian is transformed in an effective and simpler one. Only one site retains the full correlation (U) while in the others acts as an internal field, the self-energy, in the framework of an alloy analogy approximation. This field, in...

Source: http://arxiv.org/abs/0901.3517v2

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Sep 22, 2013
09/13

by
N. L. Mitchell; I. G. McCarthy; R. G. Bower; T. Theuns; R. A. Crain

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(Abridged) The thermal state of the intracluster medium results from a competition between gas cooling and heating. The heating comes from two distinct sources: gravitational heating from the collapse of the dark matter halo and thermal input from galaxy/black hole formation. However, a long standing problem has been that cosmological simulations based on smoothed particle hydrodynamics (SPH) and Eulerian mesh codes predict different results even when cooling and galaxy/black hole heating are...

Source: http://arxiv.org/abs/0812.1750v2

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Sep 21, 2013
09/13

by
R. Windmolders

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The strange quark helicity distribution Delta s(x)is derived at LO from the semi-inclusive and inclusive spin asymmetries measured by the COMPASS experiment at CERN. The significance of the results is found to depend critically on the ratio of the sbar and u quark fragmentation functions into positive kaons.

Source: http://arxiv.org/abs/0901.3690v1

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Sep 21, 2013
09/13

by
Onsi Fakhouri; Chung-Pei Ma

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In an earlier paper we quantified the mean merger rate of dark matter haloes as a function of redshift z, descendant halo mass M0, and progenitor halo mass ratio xi using the Millennium simulation of the LCDM cosmology. Here we broaden that study and investigate the dependence of the merger rate of haloes on their surrounding environment. A number of local mass overdensity variables, both including and excluding the halo mass itself, are tested as measures of a halo's environment. The simple...

Source: http://arxiv.org/abs/0808.2471v2

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Sep 22, 2013
09/13

by
Claudio Coriano; Marco Guzzi; Nikos Irges; Antonio Mariano

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We analyze the conditions under which some supersymmetric generalizations of a class of models descending from string theory allow an axion in the physical spectrum, due to the presence of anomalous abelian gauge interactions. The gauge structure of these constructions involve the Stueckelberg supermultiplet and a supersymmetric version of the Wess-Zumino term for anomaly cancellation. While these conditions are not satisfied by the MSSM superpotential, we show that an axion-like particle...

Source: http://arxiv.org/abs/0811.0117v2

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Sep 21, 2013
09/13

by
X. Q. Huang

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In this paper, we develop a unified theory for describing Hall effect in various electronic systems based on a pure electron picture (without the hole concept). We argue that the Hall effect is the magnetic field induced symmetry breaking of the charge carrier's spatial distribution. Due to the interaction of the charge carriers and the ion lattice, there are two possible symmetry breaking mechanisms which cause different signs of Hall coefficient in a Hall material. The scenario provides an...

Source: http://arxiv.org/abs/0901.3694v1

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Sep 21, 2013
09/13

by
D. A. Garcia-Hernandez; K. H. Hinkle; David. L. Lambert; K. Eriksson

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We present high-resolution (R~50,000) observations of near-IR transitions of CO and CN of the five known hydrogen-deficient carbon (HdC) stars and four R Coronae Borealis (RCB) stars. We perform an abundance analysis of these stars by using spectrum synthesis and state-of-the-art MARCS model atmospheres for cool hydrogen-deficient stars. Our analysis confirms reports by Clayton and colleagues that those HdC stars exhibiting CO lines in their spectrum and the cool RCB star S Aps are strongly...

Source: http://arxiv.org/abs/0901.3667v1

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Sep 21, 2013
09/13

by
Martin Zeppenfeld

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Analytical solutions to the wave equation in spheroidal coordinates in the short wavelength limit are considered. The asymptotic solutions for the radial function are significantly simplified, allowing scalar spheroidal wave functions to be defined in a form which is directly reminiscent of the Laguerre-Gaussian solutions to the paraxial wave equation in optics. Expressions for the Cartesian derivatives of the scalar spheroidal wave functions are derived, leading to a new set of vector...

Source: http://arxiv.org/abs/0901.3662v1

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Sep 22, 2013
09/13

by
Fariel Shafee

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We discuss a special aspect of agents placed in a social network. If an agent can be seen as comprising many components, the expressions and interactions among these components may be crucial. We discuss the role of patterns within the environment as a mode of expression of these components. The stability and identity of an agent is derived as a function of component and component-pattern identity. The agent is then placed in a specific social network within the environment, and the enigmatic...

Source: http://arxiv.org/abs/0901.3772v1

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Sep 21, 2013
09/13

by
Massimiliano Di Ventra; Yuriy V. Pershin; Leon O. Chua

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We extend the notion of memristive systems to capacitive and inductive elements, namely capacitors and inductors whose properties depend on the state and history of the system. All these elements show pinched hysteretic loops in the two constitutive variables that define them: current-voltage for the memristor, charge-voltage for the memcapacitor, and current-flux for the meminductor. We argue that these devices are common at the nanoscale where the dynamical properties of electrons and ions...

Source: http://arxiv.org/abs/0901.3682v1

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Sep 22, 2013
09/13

by
Georges Parfionov; Romàn R. Zapatrin

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For a mixed quantum state with density matrix $\rho$ there are infinitely many ensembles of pure quantum states, which average to $\rho$. Starting from Laplace principle of insufficient reason (not to give \emph{a priori} preference to any particular state), we derive a `natural' distribution of pure states averaging to $\rho$, which is `more spread' than all the others.

Source: http://arxiv.org/abs/0901.3771v1

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Sep 21, 2013
09/13

by
Jean-Paul Allouche; Narad Rampersad; Jeffrey Shallit

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We revisit a technique of S. Lehr on automata and use it to prove old and new results in a simple way. We give a very simple proof of the 1986 theorem of Honkala that it is decidable whether a given k-automatic sequence is ultimately periodic. We prove that it is decidable whether a given k-automatic sequence is overlap-free (or squareefree, or cubefree, etc.) We prove that the lexicographically least sequence in the orbit closure of a k-automatic sequence is k-automatic, and use this last...

Source: http://arxiv.org/abs/0808.1657v3

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Sep 21, 2013
09/13

by
Richard K. Obousy

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The primary focus of this dissertation is the study of the Casimir effect and the possibility that this phenomenon may serve as a mechanism to mediate higher dimensional stability, and also as a possible mechanism for creating a small but non-zero vacuum energy density. In chapter one we review the nature of the quantum vacuum and discuss the different contributions to the vacuum energy density arising from different sectors of the standard model. Next, in chapter two, we discuss cosmology and...

Source: http://arxiv.org/abs/0901.3640v1

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Sep 21, 2013
09/13

by
M. Shifman; M. Unsal

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The center-stabilized multiflavor QCD* theories formulated on R_3 x S_1 exhibit both Abelian and non-Abelian confinement as a function of the S_1 radius, similar to the Seiberg-Witten theory as a function of the mass deformation parameter. For sufficiently small number of flavors and small r(S_1), we show occurence of a mass gap in gauge fluctuations, and linear confinement. This is a regime of confinement without continuous chiral symmetry breaking (\chi SB). Unlike one-flavor theories where...

Source: http://arxiv.org/abs/0901.3743v1

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Sep 22, 2013
09/13

by
Christos Argyropoulos; Efthymios Kallos; Yan Zhao; Yang Hao

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We examine several ways to manipulate the loss in electromagnetic cloaks, based on transformation electromagnetics. It is found that, by utilizing inherent electric and magnetic losses of metamaterials, perfect wave absorption can be achieved based on several popular designs of electromagnetic cloaks. A practical implementation of the absorber, consisting of ten discrete layers of metamaterials, is proposed. The new devices demonstrate super-absorptivity over a moderate wideband range, suitable...

Source: http://arxiv.org/abs/0811.4411v2

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Sep 22, 2013
09/13

by
G. Bertaina; S. Giorgini

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On the basis of the phase diagram of the uniform system we calculate the density profiles of a trapped polarized Fermi gas at zero temperature using the local density approximation. By varying the overall polarization and the interaction strength we analyze the appearance of a discontinuity in the profile, signalling a first order phase transition from a superfluid inner core to a normal outer shell. The local population imbalance between the two components and the size of the various regions...

Source: http://arxiv.org/abs/0811.1873v2

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Sep 21, 2013
09/13

by
Petr Hajek; Antonin Prochazka

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Let $X$ be a WCG Banach space admitting a $C^k$-Fr\' echet smooth norm. Then $X$ admits an equivalent norm which is simultaneously $C^1$-Fr\' echet smooth, LUR, and a uniform limit of $C^k$-Fr\' echet smooth norms. If $X=C([0,\alpha])$, where $\alpha$ is an ordinal, then the same conclusion holds true with $k=\infty$.

Source: http://arxiv.org/abs/0901.3623v1

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Sep 18, 2013
09/13

by
Hiroyuki Chihara

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We discuss the boundedness of Berezin-Toeplitz operators on a generalized Segal-Bargmann space (Fock space) over the complex $n$-space. This space is characterized by the image of a global Bargmann-type transform introduced by Sj\"ostrand. We also obtain the deformation estimates of the composition of Berezin-Toeplitz operators whose symbols and their derivatives up to order three are in the Wiener algebra of Sj\"ostrand. Our method of proofs is based on the pseudodifferential...

Source: http://arxiv.org/abs/0806.0193v3

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Sep 22, 2013
09/13

by
Mihran Papikian

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We study the action on the Bruhat-Tits tree of unit groups of maximal orders in certain quaternion algebras over $\mathbb{F}_q(T)$ and discuss applications to arithmetic geometry and group theory.

Source: http://arxiv.org/abs/0901.3735v1

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Sep 22, 2013
09/13

by
David A. Powell; Ilya V. Shadrivov; Yuri S. Kivshar

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We study parametric amplification in nonlinear left-handed transmission lines, which serve as model systems for nonlinear negative index metamaterials. We experimentally demonstrate amplification of a weak pump signal in three regimes: with the signal in the left-handed band, with the signal in the stop band, and with the signal at a defect frequency. In particular, we demonstrate the amplification of the incident wave by up to 15dB in the left-handed regime.

Source: http://arxiv.org/abs/0812.2945v2

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Sep 22, 2013
09/13

by
Rupa Chatterjee; Lusaka Bhattacharya; Dinesh K. Srivastava

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We introduce the seminal developments in the theory and experiments of electromagnetic probes for the study of the dynamics of relativistic heavy ion collisions and quark gluon plasma.

Source: http://arxiv.org/abs/0901.3610v1

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Sep 21, 2013
09/13

by
Joyee Ghosh; R. Ghosh; F. Goldfarb; J. -L. Le Gouët; F. Bretenaker

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We present a realistic theoretical treatment of a three-level $\Lambda$ system in a hot atomic vapor interacting with a coupling and a probe field of arbitrary strengths, leading to electromagnetically-induced transparency and slow light under the two-photon resonance condition. We take into account all the relevant decoherence processes including col5Blisions. Velocity-changing collisions (VCCs) are modeled in the strong collision limit effectively, which helps in achieving optical pumping by...

Source: http://arxiv.org/abs/0901.3790v1

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Sep 22, 2013
09/13

by
W. E. Harris; M. Mouhcine; M. Rejkuba; R. Ibata

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We use deep images taken with the Advanced Camera for Surveys on board the Hubble Space Telescope of the disk galaxy NGC 891, to search for globular cluster candidates. This galaxy has long been considered to be a close analog in size and structure to the Milky Way and is nearly edge-on, facilitating studies of its halo population. These extraplanar ACS images, originally intended to study the halo field-star populations, reach deep enough to reveal even the faintest globular clusters that...

Source: http://arxiv.org/abs/0901.3733v1

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Jul 20, 2013
07/13

by
Yong Li; Ying-Dan Wang; Fei Xue; C. Bruder

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We propose a quantum description of the cooling of a micromechanical flexural oscillator by a one-dimensional transmission line resonator via a force that resembles cavity radiation pressure. The mechanical oscillator is capacitively coupled to the central conductor of the transmission line resonator. At the optimal point, the micromechanical oscillator can be cooled close to the ground state, and the cooling can be measured by homodyne detection of the output microwave signal.

Source: http://arxiv.org/abs/0804.4766v2

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Sep 18, 2013
09/13

by
Caroline J. Klivans; Kathryn L. Nyman; Bridget E. Tenner

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We study degree sequences for simplicial posets and polyhedral complexes, generalizing the well-studied graphical degree sequences. Here we extend the more common generalization of vertex-to-facet degree sequences by considering arbitrary face-to-flag degree sequences. In particular, these may be viewed as natural refinements of the flag f-vector of the poset. We investigate properties and relations of these generalized degree sequences, proving linear relations between flag degree sequences in...

Source: http://arxiv.org/abs/0806.4012v2

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Sep 21, 2013
09/13

by
Alejandro Aviles Cervantes; Jorge L. Cervantes-Cota

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We present some exact solutions and a phase space analysis of metric $f(R)$-gravity models of the type $R^{n}$. We divide our discussion in $n\neq2$ and $n=2$ models. The later model is a good approximation, at late times to the $f(R) = \frac{2}{\pi}R \tan^{-1}(R/\beta^2)$ gravity model, being this an example of a non--singular case. For $n \neq 2$ models we have found power law solutions for the scale factor that are attractors and that comply with WMAP 5-years data if $n

Source: http://arxiv.org/abs/0901.3722v1

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Sep 23, 2013
09/13

by
Chun-Yu Lin; Chopin Soo

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An obstruction to the implementation of spatially flat Painleve-Gullstrand(PG) slicings is demonstrated, and explicitly discussed for Reissner-Nordstrom and Schwarzschild-anti-deSitter spacetimes. Generalizations of PG slicings which are not spatially flat but which remain regular at the horizons are introduced. These metrics can be obtained from standard spherically symmetric metrics by physical Lorentz boosts. With these generalized PG metrics, problematic contributions to the imaginary part...

Source: http://arxiv.org/abs/0810.2161v2

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Sep 22, 2013
09/13

by
Xue-Mei Deng; Yi Xie; Tian-Yi Huang

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A gravity theory called scalar-tensor-vector gravity (STVG) has been recently developed and succeeded in solar system, astrophysical and cosmological scales without dark matter [J. W. Moffat, J. Cosmol. Astropart. Phys. 03, 004 (2006)]. However, two assumptions have been used: (i) $B(r)=A^{-1}(r)$, where $B(r)$ and $A(r)$ are $g_{00}$ and $g_{rr}$ in the Schwarzschild coordinates (static and spherically symmetric); (ii) scalar field $G=Const.$ in the solar system. These two assumptions actually...

Source: http://arxiv.org/abs/0901.3730v1

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Sep 21, 2013
09/13

by
Nicolas Ressayre

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We give a new geometric proof of a conjecture of Fulton on the Littlewood-Richardson coefficients. This conjecture was firstly proved by Knutson, Tao and Woodward using the Honeycomb theory. A geometric proof was given by Belkale. Our proof is based on the geometry of Horn's cones.

Source: http://arxiv.org/abs/0901.3633v1

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Sep 21, 2013
09/13

by
Michael Hochman

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We prove a ratio ergodic theorem for non-singular free $Z^d$ and $R^d$ actions, along balls in an arbitrary norm. Using a Chacon-Ornstein type lemma the proof is reduced to a statement about the amount of mass of a probability measure that can concentrate on (thickened) boundaries of balls in $R^d$. The proof relies on geometric properties of norms, including the Besicovitch covering lemma and the fact that boundaries of balls have lower dimension than the ambient space. We also show that for...

Source: http://arxiv.org/abs/0901.3605v1

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Sep 22, 2013
09/13

by
J. Brzozowski; E. Grant; J. Shallit

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A famous theorem of Kuratowski states that in a topological space, at most 14 distinct sets can be produced by repeatedly applying the operations of closure and complement to a given set. We re-examine this theorem in the setting of formal languages, where closure is either Kleene closure or positive closure. We classify languages according to the structure of the algebra they generate under iterations of complement and closure. We show that there are precisely 9 such algebras in the case of...

Source: http://arxiv.org/abs/0901.3761v1

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Sep 21, 2013
09/13

by
Zhen Lei; Chun Liu; Yi Zhou

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We prove the existence of both local and global smooth solutions to the Cauchy problem in the whole space and the periodic problem in the n-dimensional torus for the incompressible viscoelastic system of Oldroyd-B type in the case of near equilibrium initial data. The results hold in both two and three dimensional spaces. The results and methods presented in this paper are also valid for a wide range of elastic complex fluids, such as magnetohydrodynamics, liquid crystals and mixture problems.

Source: http://arxiv.org/abs/0901.3658v1

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41

Sep 21, 2013
09/13

by
Monica Conti; Vittorino Pata

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This note is focused on a novel technique in order to establish the boundedness in more regular spaces for global attractors of dissipative dynamical systems, without appealing to uniform-in-time estimates. As an application of the abstract result, the semigroup generated by the strongly damped wave equation $$u_{tt}-\Delta u_t-\Delta u+\phi(u)=f$$ with critical nonlinearity is considered, whose attractor is shown to possess the optimal regularity.

Source: http://arxiv.org/abs/0901.3607v1

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30

Sep 21, 2013
09/13

by
Fariel Shafee

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The role of perception in conscious behavior and decision-making is examined. The effect of spatial and temporal stochasticity in the acquisition of beliefs is discussed. The idea of an agent as a locally strongly coupled group of states leads to the creation of energy minima in an interaction potential landscape. The interaction of such agent states and environment states acting at different levels of complexity and scale, subject to stochastically expressed interaction interfaces, may lead to...

Source: http://arxiv.org/abs/0901.3793v1

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30

Sep 21, 2013
09/13

by
Shrinivas Kudekar; Nicolas Macris

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Consider transmission over a binary additive white gaussian noise channel using a fixed low-density parity check code. We consider the posterior measure over the code bits and the corresponding correlation between two codebits, averaged over the noise realizations. We show that for low enough noise variance this average correlation decays exponentially fast with the graph distance between the code bits. One consequence of this result is that for low enough noise variance the GEXIT functions...

Source: http://arxiv.org/abs/0901.3630v1